Borospherene

Despite many calculation-based investigations into its structure and properties, a viable route for the synthesis and isolation of borospherene has yet to be established, and as a consequence it is still relatively poorly understood.

In 2014, the first experimental evidence of a homoelemental fullerene-like B40 cluster was reported by Zhai et al., after decades of theoretical investigations into boron cage structures following the discovery of buckminsterfullerene.

[5] Anionic B40− clusters were transiently produced by laser vaporisation of a 10B-enriched boron disc target, and studied with photoelectron spectroscopy.

Neutral borospherene has a large HOMO-LUMO gap of 3.13 eV (which destabilises its anion, making the ground state of B40− the quasi-planar isomer).

The simulated spectra of two energetically lowest-lying isomers of the anion - a sheet-like structure and a closed cage - were found to fit experimental data well.

[1] The structure of the cage is not perfectly uniform – "Several atoms stick out a bit from the others, making the surface of borospherene somewhat less smooth than a buckyball" according to Wang.

[11] Optimisation of (AM)6B40 structures (AM = Li, Na, K) revealed the metal atoms to be distributed above the centres of each hexagon and heptagon of B40, with a large binding energy in each case suggesting these complexes should be stable.

[12] Modelling an exohedral Ca6B40, Esrafili et al. simulated carbon dioxide adsorption to the complex and found the upper bound of adsorption to be four CO2 molecules per Ca, with an average binding energy of -0.54 eV each - falling within the optimal range of binding energies for a CO2 adsorbent (0.40 - 0.80 eV), allowing facile desorption at elevated temperatures.